"Juan Mata has arrived at the Aon Training Complex to begin his medical," the club said on Twitter.

The deal is set to eclipse the STG30.75 million ($F96m) that United paid Tottenham Hotspur in 2008 to sign Bulgarian striker Dimitar Berbatov.

Mata joined Chelsea from Valencia in 2011 and was voted the club's player of the year in his first two seasons, but he has fallen out of favour since Jose Mourinho returned to Stamford Bridge as manager last year.

Pending the completion of the transfer, Mata is expected to go straight into the squad for United's home game against Cardiff City in the league on Tuesday.

His signing reflects Moyes's eagerness to arrest a startling decline in United's fortunes since the Scot succeeded Alex Ferguson as manager at the end of last season.

Meanwhile, reports in the British media yesterday claimed that United have opened talks with striker Wayne Rooney over a new contract.

The 28-year-old England striker has 18 months remaining on his current deal and was the subject of two unsuccessful bids from Chelsea during the close season.